Mycelial growth of the snow mold fungus, Sclerotinia borealis, improved at low water potentials: an adaption to frozen environment

Abstract

The snow mold fungus, Sclerotinia borealis, shows optimal growth at 4°C on potato dextrose agar (PDA) and can grow even at subzero temperature. Its mycelial growth was improved on frozen PDA at -1°C and on PDA containing potassium chloride (KCl) (water potential, -4.27 to -0.85 MPa) or D(-) sorbitol (-3.48 to -0.92 MPa). Its optimal growth temperature shifted from 4 to 10°C on PDA amended with KCl or sorbitol, indicating that inherent optimal growth occurs at high temperatures. These results suggest that S. borealis uses concentrated nutrients in the frozen environment and that such physiologic characteristics are critical for the fungus to prevail at subzero temperatures.

Environments influence the psychrophily of fungi and oomycetes in the cryosphere

“…His experiments were not made under controlled conditions and have not been reproduced by others. Under controlled conditions, we confirmed his results that S. borealis grew on frozen PDA (Hoshino et al 2009(Hoshino et al , 2010. S. borealis showed normal mycelial growth under the frozen condition, and mycelial growth rate on frozen plates at -1°C was faster than that on unfrozen PDA at its optimal growth temperature of 4−10°C.…”

“…An increase in intracellular osmosis enhanced mycelial growth and shifted the optimal mycelial growth temperature from 10−15°C to 4°C. However, mycelial growth of other snow moulds such as Sclerotinia nivalis I. Saito and Sclerotinia trifoliorum Erikss was inhibited at low water potential (Hoshino et al 2009(Hoshino et al , 2010. Therefore, osmophilism of S. borealis was probably a unique feature to adapt to severe freezing.…”

Surviving freezing in plant tissues by oomycetous snow molds

“…These fungi belong to various taxa (oomycetes, ascomycetes, and basidiomycetes). Oomyceteous snow molds, Pythium species, were reported to be less tolerant to chilling [3] and freezing temperatures than other snow mold taxa [1,2,5,10]. However, Pythium species have often caused snow mold disease on mosses in Polar Regions [11,12].…”

The 203 kbp Mitochondrial Genome of the Phytopathogenic Fungus Sclerotinia borealis Reveals Multiple Invasions of Introns and Genomic Duplications

“…S. borealis is a psychrophilic necrotrophic fungus with an optimum growth temperature between 4°C and 10°C [1]. The main specific feature of the disease called “snow mould” is a white mycelium and sclerotia growth on dead plant tissues [2].…”